This invention relates to circulatory assist systems and more particularly to actuating units for driving blood pumps in circulatory assist systems.
The advent of open heart surgery has presented to the medical profession the opportunity of repairing damaged or diseased hearts of individuals and where appropriate, using circulatory assist systems in individuals who, without such correction and/or systems, face premature death. Many devices are involved in this type of surgery. For example, one type of circulatory assist system comprises an auxiliary ventricle or valveless blood pump connected across the arch of the aorta and is driven by fluid pressure in response to electronic signals (QRS wave) provided by the heart itself. By operating the blood pump or auxiliary ventricle in proper phase, the systolic pressure in the left heart can be reduced and the systemic circulation can be maintained with a substantially reduced work load on the heart muscle. In addition, the operation of the auxiliary ventricle has the effect of shifting the phase of the normal systolic pressure so that this pressure appears in the aorta at a time when the left ventricle is relaxed. Assuming competence of the normal aortic valve, one then has an increased perfusion pressure available to the coronary arteries. It is believed that such an increase in coronary perfusion, together with a reduction in the effort required from the heart, should be effective in a number of cases of cardiac insufficiency.
Another circulatory assist system presently used to some considerable extent is one utilizing intro-arterial balloon pumping. In this technique an inflatable intra-arterial device or "balloon" on a catheter is typically inserted through a femoral artery and passed up the arterial tree into the decending aorta. When in place in the aorta, the balloon is sequentially inflated and deflated to provide the necessary circulatory assistance. For a description of such a balloon and typical prior art systems associated therewith, reference is made to U.S. Pat. Nos. 3,452,738, issued July 1, 1969, 3,456,444, issued July 22, 1969, and 3,504,662, issued Apr. 7, 1970, which are incorporated herein as if set out at length.
Other techniques are known and include left-heart bypass and diastolic augmentation.
As may be seen from the above, one important component of circulatory assist systems is a pump that either assumes the heart's role of pumping blood or which reduces the work load of the heart muscle. By using heart pump equipment for extended periods of time, it is contemplated that the equipment may be utilized for regional perfusions in therapeutic treatment of the heart. Still another use of such equipment is to provide circulation of blood through an artificial organ such as an external artificial kidney. In connection with this function of the apparatus, it should be noted that many research institutions at this time are concentrating their research activities on providing artificial counterparts of other organs, and whenever such application requires circulation, the present invention may be utilized.
In the use of circulatory assist systems, it is desirable if not necessary to be able to control the blood pump through an actuating unit that is pneumatically operated to eject an operating fluid to drive the blood pump in a manner to meet the requirements of a patient's circulatory system. The actuating unit embodied in the present invention satisfies all of the requirements for an actuating unit set forth above and has been proved successful in carrying out the difficult task of driving a blood pump under various types of conditions.
Accordingly, it is an object of the present invention to provide an actuating unit for driving a blood pump.
Another object of the present invention is to provide an actuating unit that is simple in construction and operation and that is not susceptible to breakdown.
A further object of the present invention is to provide an automatically operated actuating unit for operating a heart pump wherein the actuator is adapted to control a hydraulic pulse for actuating a pump unit or ventricle to move an equal volume of blood through or past the blood pumping unit.
A still further object of the invention is to provide an actuating unit in a circulatory assist system that is simple in construction, quiet in operation, requires a minimum amount of power to operate and that will accurately and consistently provide selectable different volumetric displacements for driving different size blood pumps.